The present invention relates to flat panel displays. More particularly, the present invention relates to systems for backlighting flat panel displays.
The principle of operation of flat panel displays is well-known in the art. However, for purposes of understanding the present invention it can be stated that flat panel displays, such as liquid crystal displays (LCDs), operate by reducing the transmissibility of light through a matrix of xe2x80x9cpixelxe2x80x9d elements when an electric field is applied. Since the effect is localized to selected pixel elements, shapes and characters can be drawn by carefully controlling the application of the electric field. Unlike cathode ray tubes, non-emissive flat panel displays are not self-illuminating. Therefore, some sort of backlighting of the flat panel display pixel matrix is typically required in order for the flat panel display to be viewed.
The design and development of high performance luminaires (backlights) for flat panel display applications presents the continuous challenge of providing more luminance and luminance uniformity, while maintaining the smallest profile depth possible. Larger displays make these requirements increasingly difficult given the current lamp technologies available. Further, the need for larger lamps, which dissipate higher levels of arc power, often results in greater difficulty with respect to thermal management of the optical components of the display.
Typically, backlighting is accomplished by locating one or more fluorescent lamps or lamp sections in a sealed cavity behind the flat panel display pixel matrix. A diffuser is generally located between the matrix and the one or more lamp sections in order to facilitate viewing of the flat panel display from a variety of angles.
Light generated by the lamps can be lost in a number of different manners. For instance, a large share of the light generated from a particular lamp section is radiated from the sides of the lamp section towards adjacent lamp sections. A significant portion of the light radiated into adjacent lamp sections is not recovered for use in backlighting the display matrix. This type of loss is sometimes referred to as lamp-to-lamp absorption. The loss of light associated with lamp-to-lamp absorption plays a role in non-uniformity of luminance provided by the backlight, while at the same time resulting in the need for additional backlighting power to adequately illuminate the display matrix. This in turn has a adverse effect on the thermal management of the flat panel display.
A luminaire for back lighting a flat panel display in accordance with the present invention includes a fluorescent lamp having multiple lamp sections and a stack of optical components. A light guide is positioned between the fluorescent lamp and the stack of optical components. The light guide includes a first section extending across a width of the luminaire which separates the multiple lamp sections from the stack of optical components and which is adapted to substantially uniformly distribute light from the multiple lamp sections toward the stack of optical components. The light guide also includes multiple leg sections each adapted to protrude from the first section of the light guide to positions between adjacent lamp sections or to positions between one of the lamp sections and a side wall. The multiple leg sections of the light guide redirect light from the lamp sections into the first section of the light guide.